A rotary encoder of the prior art has a structure where a movable contact and a stationary contact are disposed on a plane orthogonal to an axis of rotation of the movable contact, and an operating axle is mounted in a position coaxial with the axis of rotation of the movable contact, so that the operating axle is movable only in a direction of the rotation of the axis of rotation, or in the direction of rotation and a direction of the axis.
A rotary encoder equipped with a push switch will be described hereinafter, by referring to FIG. 13, which depicts a partial sectional front view and is representative of a conventional rotary encoder of this kind.
In FIG. 13, an operating axle 31 is inserted into a circular hole 32A of a bearing 32 from underneath it, and a center circular portion 31A is held fitted in the circular hole 32A in a manner that the operating axle 31 is rotatable as well as vertically movable. A thin non-circular spindle 31B at a lower end of the operating axle 31 fits into a non-circular hole 33A in a center of a rotary contact board 33 in such a manner that a rotary movement of the operating axle 31 is transferred to the rotary contact board 33 whereas a vertical movement is not.
The rotary contact board 33 stays in its vertical position by being held between the bearing 32 and a case 34 beneath the rotary contact board 33. The rotary contact board 33 is provided on its lower surface with a contact plate 35 by an insert molding. The contact plate 35 includes a center ring portion 35A and a plurality of rectangular web portions 35B extending radially from the center ring portion 35A, as shown in FIG. 14.
Three flexible contacts 36A, 36B and 36C, all serving as stationary contacts, extending from the case 34 stay in resilient contact with the center ring portion 35A and the rectangular web portions 35B of the contact plate 35 respectively, and all of the above elements constitute a contact portion of an encoder unit. The flexible contacts 36B and 36C corresponding to the rectangular web portions 35B are so positioned that they are slightly shifted with each other in a direction of the rotation.
Further, a push switch 37 is disposed under the case 34, and a lower end 31C of the operating axle 31 locates in contact with an upper end of a push button 37A of the push switch 37.
Operation of the rotary encoder equipped with a push switch will now be described hereinafter. When an operating knob 39 attached to an upper end 31D of the operating axle 31 is rotated, it turns the operating axle 31 and therefore the rotary contact board 33. Among the three flexible contacts 36A, 36B and 36C placed against the contact plate 35 on the lower surface of the rotary contact board 33, the flexible contacts 36A slides resiliently on the center ring portion 35A and the flexible contacts 36B and 36C slide on the rectangular web portions 35B. As a result, the rotation generates pulse signals between the terminals 38A and 38B as well as between the terminals 38A and 38C communicating with their respective flexible contacts 36A, 36B and 36C, and thereby they function as an encoder.
In the above operation, a circuit of an apparatus, which employs this device, detects a delay in time between the pulse signals that appear between the terminals 38A and 38B, and between the terminals 38A and 38C, due to the shift in positions of the flexible contacts 36B and 36C, which are in contact with the rectangular web portions 35B of the contact plate 35. And the device is able to function according to a direction and an amount of the rotation.
Also, during the above rotating manipulation, the operating axle 31 does not move in the vertical direction, so as not to operate the push switch 37.
Next, when the operating axle 31 is moved downward by applying a depressing force to the operating knob 39 attached to the upper end 31D of the operating axle 31, as shown by an arrow in FIG. 15, i.e. a partial sectional front view of the device, the lower end 31C depresses the push button 37A to operate the push switch 37.
The encoder unit does not function by this manipulation, because the rotary contact board 33 of the encoder unit does not move downward, nor does it rotate.
However, the rotary encoder of the prior art is operative only in the direction of rotation and the direction of the axis of the operating axle 31 to which the operating knob 39 is attached. To improve accuracy of the encoder unit by increasing the resolution or to increase the number of output signals, it is necessary to increase the number of rectangular web portions 35B extended radially from the center ring portion 35A of the contact plate 35, or increase the number of flexible contacts 36B and 36C, which are so arranged as to make contact with the rectangular web portions 35B at points shifted with respect to each other. For this improvement, it is necessary to increase the width of each of the rectangular web portions 35B and insulation spaces between them. This consequently requires an extension in length of the rectangular web portions 35B toward their radial direction, and therefore an enlargement in diameter of the contact plate 35, i.e. the movable contact. This causes a substantial restriction in designing the apparatuses that employ these devices, since it increases overall dimensions of the rotary encoder, including the case 34. Because of the increased radiuses of the contacting points the sliding speed at the contacting points between the flexible contacts 36B and 36C and the rectangular web portions 35B is increased during rotating manipulation, thus giving rise to a problem that disturbances in the signal, such as fluctuations, are liable to occur at boundaries between the rectangular web portions 35B, i.e. conductive surfaces, and insulating surfaces.
An object of the present invention is to solve the foregoing problem, and to provide a rotary encoder that is capable of operating a linearly-driven type component in addition to a rotary type encoder by rotating and tilting an operating axle provided with an operating knob. The invention also provides a rotary encoder that is more accurate and capable of producing a greater number of output signals without requiring an increase in external dimensions.